From 0303e64efa8ee223c0767d7be8d2875a62b88aea Mon Sep 17 00:00:00 2001 From: Jason Zaugg Date: Mon, 25 Feb 2013 21:54:09 +0100 Subject: SI-7183 Disable unreachability for withFilter matches. This avoids spurious unreachable warnings on code that the user didn't write. The parser desugars for-comprehensions such as: for (A(a) <- List(new A)) yield a To: List(new A()).withFilter(((check$ifrefutable$2) => check$ifrefutable$2: @scala.unhecked match { case A((a @ _)) => true case _ => false }) ) But, if `A.unapply` returns `Some[_]`, the last case is dead code. (Matching against a regular case class *would* fall through in the caes of a null scrutinee.) In SI-6902, we enabled unreachability warnings, even if the scrutinee was annotated as @unchecked. That was consistent with the 2.9.2 behaviour, it was only disabled temporarily (actually, accidentally) in 2.10.0. But, the old pattern matcher didn't warn about this code. This commit makes the pattern matcher recognise the special scrutinee based on its name and disables both exhaustivity *and* unreachability analysis. To do so, the we generalize the boolean flag `unchecked` to the class `Suppression`. --- .../tools/nsc/typechecker/PatternMatching.scala | 42 ++++++++++++++-------- 1 file changed, 28 insertions(+), 14 deletions(-) (limited to 'src') diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala index f7579ad249..87fe3fb3f6 100644 --- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala +++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala @@ -936,7 +936,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // the making of the trees /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// trait TreeMakers extends TypedSubstitution { self: CodegenCore => - def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type, unchecked: Boolean): (List[List[TreeMaker]], List[Tree]) = + def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type, supression: Suppression): (List[List[TreeMaker]], List[Tree]) = (cases, Nil) def emitSwitch(scrut: Tree, scrutSym: Symbol, cases: List[List[TreeMaker]], pt: Type, matchFailGenOverride: Option[Tree => Tree], unchecked: Boolean): Option[Tree] = @@ -1408,18 +1408,24 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def matchFailGen = (matchFailGenOverride orElse Some(CODE.MATCHERROR(_: Tree))) patmatDebug("combining cases: "+ (casesNoSubstOnly.map(_.mkString(" >> ")).mkString("{", "\n", "}"))) - val (unchecked, requireSwitch) = - if (settings.XnoPatmatAnalysis.value) (true, false) + val (suppression, requireSwitch): (Suppression, Boolean) = + if (settings.XnoPatmatAnalysis.value) (Suppression.NoSuppresion, false) else scrut match { - case Typed(_, tpt) => - (tpt.tpe hasAnnotation UncheckedClass, - // matches with two or fewer cases need not apply for switchiness (if-then-else will do) - treeInfo.isSwitchAnnotation(tpt.tpe) && casesNoSubstOnly.lengthCompare(2) > 0) + case Typed(tree, tpt) => + val suppressExhaustive = tpt.tpe hasAnnotation UncheckedClass + val supressUnreachable = tree match { + case Ident(name) if name startsWith nme.CHECK_IF_REFUTABLE_STRING => true // SI-7183 don't warn for withFilter's that turn out to be irrefutable. + case _ => false + } + val suppression = Suppression(suppressExhaustive, supressUnreachable) + // matches with two or fewer cases need not apply for switchiness (if-then-else will do) + val requireSwitch = treeInfo.isSwitchAnnotation(tpt.tpe) && casesNoSubstOnly.lengthCompare(2) > 0 + (suppression, requireSwitch) case _ => - (false, false) + (Suppression.NoSuppresion, false) } - emitSwitch(scrut, scrutSym, casesNoSubstOnly, pt, matchFailGenOverride, unchecked).getOrElse{ + emitSwitch(scrut, scrutSym, casesNoSubstOnly, pt, matchFailGenOverride, suppression.exhaustive).getOrElse{ if (requireSwitch) typer.context.unit.warning(scrut.pos, "could not emit switch for @switch annotated match") if (casesNoSubstOnly nonEmpty) { @@ -1436,7 +1442,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL }) None else matchFailGen - val (cases, toHoist) = optimizeCases(scrutSym, casesNoSubstOnly, pt, unchecked) + val (cases, toHoist) = optimizeCases(scrutSym, casesNoSubstOnly, pt, suppression) val matchRes = codegen.matcher(scrut, scrutSym, pt)(cases map combineExtractors, synthCatchAll) @@ -3831,11 +3837,13 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL with OptimizedCodegen with SymbolicMatchAnalysis with DPLLSolver { self: TreeMakers => - override def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type, unchecked: Boolean): (List[List[TreeMaker]], List[Tree]) = { - unreachableCase(prevBinder, cases, pt) foreach { caseIndex => - reportUnreachable(cases(caseIndex).last.pos) + override def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type, suppression: Suppression): (List[List[TreeMaker]], List[Tree]) = { + if (!suppression.unreachable) { + unreachableCase(prevBinder, cases, pt) foreach { caseIndex => + reportUnreachable(cases(caseIndex).last.pos) + } } - if (!unchecked) { + if (!suppression.exhaustive) { val counterExamples = exhaustive(prevBinder, cases, pt) if (counterExamples.nonEmpty) reportMissingCases(prevBinder.pos, counterExamples) @@ -3860,3 +3868,9 @@ object PatternMatchingStats { val patmatAnaExhaust = Statistics.newSubTimer (" of which in exhaustivity", patmatNanos) val patmatAnaReach = Statistics.newSubTimer (" of which in unreachability", patmatNanos) } + +final case class Suppression(exhaustive: Boolean, unreachable: Boolean) + +object Suppression { + val NoSuppresion = Suppression(false, false) +} \ No newline at end of file -- cgit v1.2.3